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Subject: bug#16979: Strange behavior with "grep --color=auto" with dot in expression
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Strange behavior with "grep --color=auto" with dot in expression

For some reason, ssh produces output with CRLF when there is a key
problem, and when I redirected that to a file, and used grep to search
through it, I found that it seemed like "." was not matching correctly,
but when you pipe the output to "cat", it looks as expected. And without
"--color=auto" or with unix line endings, it works fine.

$ alias grep
alias grep='grep --color=auto'
$ diff <(hexdump -C file.txt) <(hexdump -C file2.txt)
4,5c4,5
< 00000030  41 53 54 59 21 0d 0a                              |ASTY!..|
< 00000037
---
> 00000030  41 53 54 59 21 0a                                 |ASTY!.|
> 00000036
$ grep -i nasty file2.txt | grep .
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
$ grep -i nasty file.txt | grep .

$ grep -i nasty file.txt | grep . | cat
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!

$ file file*
file2.txt: ASCII text
file.txt:  ASCII text, with CRLF line terminators

I tested it in konsole and xterm, and both do the same, so I guess you
just need:

$ grep --version
grep (GNU grep) 2.14
Copyright (C) 2012 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later
<http://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Written by Mike Haertel and others, see
<http://git.sv.gnu.org/cgit/grep.git/tree/AUTHORS>.

$ bash --version
GNU bash, version 4.2.45(1)-release (x86_64-suse-linux-gnu)
Copyright (C) 2011 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later
<http://gnu.org/licenses/gpl.html>

This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

-- 

--------------------------------------------
Peter Maloney
Brockmann Consult
Max-Planck-Str. 2
21502 Geesthacht
Germany
Tel: +49 4152 889 300
Fax: +49 4152 889 333
E-mail: peter.maloney@HIDDEN
Internet: http://www.brockmann-consult.de
--------------------------------------------

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To: Peter Maloney <peter.maloney@HIDDEN>
Subject: bug#16979: Acknowledgement (Strange behavior with "grep
 --color=auto" with dot in expression)
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Date: Mon, 10 Mar 2014 15:47:03 +0000

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Subject: bug#16979: Strange behavior with "grep --color=auto" with dot in expression
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From: Paul Eggert <eggert@HIDDEN>
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This is due to the CR at the end of the line.  A simple way to reproduce 
the bug is:

printf 'X\r\n' | grep --color=always -E '(X|[[:space:]])'

This will output a line that appears to be empty.  If you filter the 
output of 'grep' through 'od -c', you'll see:

0000000 033   [   0   1   ;   3   1   m 033   [   K   X 033   [   m 033
0000020   [   K 033   [   0   1   ;   3   1   m 033   [   K  \r 033   [
0000040   m 033   [   K  \n

That is, begin color, erase to end of line, X, end color, erase to end 
of line, begin color, erase to end of line, carriage-return, end color, 
erase to end of line, linefeed.  The last "erase to end of line" erases 
the X.

As can be seen, the grep --color output is busted in this case, and is 
suboptimal in general.  Someone who cares about grep --color (which is 
not me :-) should take a look at it.

You can work around the bug by filtering out the CRs before running 
'grep', or by not using the --color option.

Last modified: Mon, 25 Nov 2019 12:00:02 UTC

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Copyright (C) 1999 Darren O. Benham, 1997 nCipher Corporation Ltd, 1994-97 Ian Jackson.